update release notes and version for desispec/0.68.1 #5774

Job	Run time
Doc test (ubuntu-latest, 3.9)	43s
API doc completeness test (ubuntu-latest, 3.9)	22s
Test coverage (ubuntu-latest, 3.10, <6, <2, <1.23)	7m 57s
Test minimal env (ubuntu-latest, 3.10)	1m 2s
Unit tests (ubuntu-latest, 3.9, ==5.0, ==1.1.6, <1.23)	6m 11s
Style check (ubuntu-latest, 3.9)	23s
Unit tests (ubuntu-latest, 3.9, ==5.0, <2, <1.23)	5m 55s
Unit tests (ubuntu-latest, 3.9, <6, ==1.1.6, <1.23)	6m 23s
Unit tests (ubuntu-latest, 3.9, <6, <2, <1.23)	5m 43s
Unit tests (ubuntu-latest, 3.10, ==5.0, ==1.1.6, <1.23)	5m 54s
Unit tests (ubuntu-latest, 3.10, ==5.0, <2, <1.23)	5m 43s
Unit tests (ubuntu-latest, 3.10, <6, ==1.1.6, <1.23)	5m 56s
Unit tests (ubuntu-latest, 3.10, <6, <2, <1.23)	5m 39s
	57m 51s

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